Understanding Lazy Evaluation & Actions

How can we construct an efficient query plan where execution is deferred until an explicit action is triggered?

Expert⏱ 3 Minutes⭐ 800 XP

🤔 THE QUESTION

How can we construct an efficient query plan where execution is deferred until an explicit action is triggered?

💡 WHAT IS IT?

Transformations build a directed acyclic graph (DAG) of execution steps without processing data until an action like write or count() runs.

🎯 WHAT IS IT USED FOR?

Enabling Catalyst optimizer to combine filters, eliminate unused columns, and prune partitions before execution.

💻 EXAMPLE

df_plan = df.filter(col("status") == "ACTIVE").select("user_id", "email")
total_active = df_plan.count()

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